A water flow detection device is a device that is provided on a pipe of fire-fighting equipment such as a sprinkler system or a foam fire-fighting system and that detects a water flow in the pipe and then outputs signals.
The water flow detection device has an inner structure of a check valve. A valve body divides the inside of the device into a primary chamber and a secondary chamber, and the check valve is normally in a closed state. The primary and secondary chambers are normally filled with water. A pipe connected to the primary chamber (hereinafter referred to as a “primary side pipe”) is connected to a water source such as a water storage tank, and a pipe connected to the secondary chamber (hereinafter referred to as a “secondary side pipe”) is connected to a dispersion head such as a sprinkler head or a form head.
The water flow detection device is provided to detect the operation of the dispersion head connected to the secondary side pipe. For example, in cases where a sprinkler head operates, water that fills the secondary side pipe is discharged from the sprinkler head with the result that the internal pressure of the secondary side pipe is reduced. Accordingly, internal pressure of the secondary chamber of the water flow detection device is decreased with the result that an effect of the pressure on the valve body enters an imbalance state. The force acting on the valve body from the side of the primary chamber exceeds the force acting on the valve body from the side of the secondary chamber with the result that the valve body opens.
The water flow detection device has a switching device that detects the opening of the valve body, and the switching device operates and then outputs signals. The output signals are connected to a monitoring apparatus installed in, for example, an administrative room of a building, and the monitoring apparatus outputs signals to inform an administrative person of the operation of the sprinkler head.
A typical example of such a water flow detection device is known, which has a configuration including: a valve body having a valve body that employs a structure of a swing check valve; a detection rod that moves in conjunction with the opening of the valve body; and a switch that is provided outside of the valve body and that detects the movement of the detection rod to output signals, the movement being in conjunction with the opening of the valve body (for example, see Patent Document 1).
As illustrated in FIG. 14, the water flow detection device disclosed in the Patent Document 1 has a rotational arm 31, as a detection rod, that is provided in the form of a rod and that serves so as to operate a switch. An end of the rotational arm 31 has a paddle portion 31b that contacts an upper portion of a valve body D, and another end of the rotational arm 31 protrudes to the outside of the valve body and has a switch cam portion 31c. A reed switch 35 that is capable of outputting signals is provided in the vicinity of the switch cam portion 31c. The rotational arm 31 is supported by a rotational shaft 32 that is horizontally disposed between the valve body and the reed switch 35. In cases where the paddle portion 31b moves in response to the opening of the valve body D, the rotational arm 31 rotates around the rotational shaft 32, so that the switch cam portion 31c operates the reed switch 35.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-55400